Mechanical behavior of ultra-high performance concrete (UHPC) using recycled fine aggregate cured under different conditions and the mechanism based on integrated microstructural parameters

摘要

Mechanical behavior of ultra-high performance concrete (UHPC) using recycled fine aggregate (RFA) was experimentally investigated. It was found that the compressive and flexural strength and tenacity of UHPC decreased as more RFA was introduced, but were enhanced by the autoclaved curing. The total length of the diverse types of interfacial transition zones (ITZs) was found to increase along with the growth of RFA replacement ratios; the quality of ITZs was improved by the autoclaved curing. This paper integrated the geometric and mechanical properties of ITZs and the other material phases on the micro scale to propose two ITZ parameters, psi(1), psi(2), and a more comprehensive microstructural parameter, psi(3). Based on correlation analysis, psi(3) was proved to be more reliable in describing the key microstructural features of UHPC prepared with RFA, and also in quantitatively revealing the mechanism for the mechanical behaviour of UHPC on the macro scale, regardless of the RFA dosages or curing conditions. (C) 2018 Elsevier Ltd. All rights reserved.